Self-regulating weirs and fishways

ABSTRACT

A self-regulating tilting weir comprises a tiltable weir gate over which the water flows, the weir gate being hinged at its lower edge ( 3 ) to the base of a support frame ( 1 ) and counterbalanced by floats ( 4 ) located upstream of the weir gate so that the level of water is raised in response to a fall in the water level upstream of the weir gate and is lowered in response to an increase in the water level upstream of the weir gate, the weir gate being connected to the floats ( 4 ) by chains or cables ( 5 ) which pass over pulley wheels ( 6 ), and devices ( 7, 8 ) being provided for effecting vertical movement of the pulley wheels ( 6 ) relative to the support frame ( 1 ). A self-regulating fishway (FIGS.  9  to  11 ) is provided alongside the weir.

FIELD OF THE INVENTION

This invention relates to self-regulating weirs and fishways.

Water control structures are well known devices, variously known assluices, penstocks, gates or weirs, which control the flow of water bymeans of fixed or moving barriers. There is a special type of weir,known as a tilting or pivoted weir, in which the water flow is regulatedby an inclined plane adjusted to different heights according to theupstream water level that is required. The dammed water builds up to therequired level, before flowing over the edge of the weir to a lowerlevel.

Water flow can, however, be erratic over any given period and frequentadjustment of a tilting weir can become necessary to suit changingconditions, particularly in order to release maximum flow in the case offlash floods. Also, by nature of its function, the weir may be difficultof access and distant from service facilities.

Ideally, therefore, a tilting or pivoted weir should meet the followingrequirements:

a) automatic self-regulation of water flow,

b) simple adjustment to vary the controlled water level that isrequired,

c) automatic response to flood or drought conditions,

d) automatic response to release floating clogging material,

e) availability of manual override,

f) mechanical operation independent of any external power source,

g) simple components requiring minimum attention,

h) the control gear should not be subject to abrasion or clogging bywaterborne or submerged detritus,

i) facility to flush out submerged detritus,

j) the upstream level control has priority over downstream level,

k) all operations must be safe to use by a lone operator, and

l) there should be a facility for migratory fish movement.

It is an object of a first aspect of the present invention to provide animproved form of tilting or pivoted weir. It is a more specific objectof said first aspect of the present invention to provide an improvedform of self-regulating tilting or pivoted weir which meets all orsubstantially all of the above requirements.

In my British Patent Specification No. 2 294 079B, to which referenceshould be made, there is described and claimed a counterbalanced,self-regulating tilting weir comprising a tiltable weir gate over whichthe water flows, the weir gate being hinged at its lower edge to thebase of a rectangular support frame and counterbalanced by float meanslocated upstream of the weir gate so that the level of the weir israised in response to a fall in the water level upstream of the weirgate and is lowered in response to an increase in the water levelupstream of the weir gate, the weir gate being connected to the floatmeans by chains which pass over sprockets mounted on an operating shaftcarried by the frame, and means being provided for manual operation ofthe weir, over-riding the action of the float means and locking the weirgate in a desired position regardless of the water level.

It is a further object of the first aspect of the present invention toprovide improvements in the tilting weir described and claimed in PatentSpecification No. 2 294 079.

A second aspect of the present invention is concerned with the provisionof a self-regulating fishway, allowing migratory fish to pass by anobstruction despite variations in river level upstream and downstream ofthe obstruction. If fluctuations in flow are excessive then aself-regulating tilting or pivoted weir can be used in parallel with thefishway to moderate the variations in water level to suit theself-regulating fishway.

Channels specifically designed to allow migratory fish to pass anobstruction are referred to herein as fishways. The most common fishpass profiles to be installed in fishway channels are of the verticalslot, Denil, or pool and weir type. Although there are other fishpassage profiles in use throughout the world, the present invention isconcerned primarily with fishways incorporating the proven profiles anddimensional relationships of the fish pass profiles referred to above.

Fishways are normally a fixture with an incline determined by thelocation and the habits of the local fish species. However, as mentionedabove, river flows can be erratic for many different reasons and produceconstantly changing levels. If a fishway is a fixture, it can beinundated as a result of excessive flow or can become ineffective if theupstream water level falls below the entrance sill. A manuallyadjustable entrance sill level may require frequent adjustment, whilethe location and function of the fishway can make it remote from aservice base, with difficult access.

General elements of fishway/fish pass efficiency which are recognised asimportant to their design include the following:

a) the need to optimise the speed and success of fish passage tominimise delay, stress, damage and fallback of the fish,

b) the need to minimise water use where there are competing waterrequirements,

c) the need to maximise the range of stream flow under which the fishwayis operable by matching the fish pass operation to flows during theperiod of desired fish passage,

d) the need to minimise construction, operation and maintenance costs byusing construction methods and materials appropriate to the remoteness,geometric, hydrologic and geologic characteristics of the site, and

e) allowance for the clearance of debris.

It is an object of the second aspect of the present invention to providean improved form of fishway, particularly a self-regulating fishwaywhich meets the above requirements.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided acounterbalanced, self-regulating tilting weir comprising a tiltable weirgate over which the water flows, the weir gate being hinged at its loweredge to the base of a support frame and counterbalanced by float meanslocated upstream of the weir gate so that the level of the weir israised in response to a fall in the water level upstream of the weirgate and is lowered in response to an increase in the water levelupstream of the weir gate, the weir gate being connected to the floatmeans by chains or cables which pass over pulley wheels, and means beingprovided for effecting vertical movement of the pulley wheels relativeto the support frame.

The means for effecting vertical movement of the pulley wheels maycomprise vertical lift spindles operated, via a worm gear, by means of aremovable hand crank.

Means are preferably provided for adjustment of the operating angles ofthe chains or cables, and the weight, number and position of thefloating counterbalances.

Means may also be provided for operating the weir manually overridingthe automatic action and fixing the weir either fully open or fullyclosed as required, regardless of the flow conditions.

According to a second aspect of the present invention there is provideda self-regulating fishway comprising a tiltable chute containing a fishpass profile, the chute being arranged for tilting movement under theaction of one or more floats positioned at or adjacent to the upstreamend of the chute so that the required relative water depth is maintainedat the chute entrance, the upstream level being so regulated that thechute incline does not exceed maximum desirable limit for the specificfish pass profile which is utilised.

The float or floats at the upstream end of the chute preferablyincorporate a submersed buoyant bulb profile extending upstream of thechute entrance. The bulb profile acts in substantially the same way asthat located just below the waterline on the bow of a modern commercialship, diverting the main force of water to either side so that themajority of floating debris is deflected from the chute entrance, whilstdesirable flow is maintained.

The flow through the self-regulating fishway is thus maintainedsubstantially constant, providing a virtually debris-free flow fromupstream and fish-attracting velocity at the downstream entrance.

Provision is preferably made for cables to be attached to both sides ofthe upstream end of the chute, the other ends of the cables beingattached to the headwall, or other convenient point, in order tomaintain the desired alignment of the fishway with the normal flow.

Regulation of the upstream water level for the self-regulating fishwayis preferably provided by means of the self-regulating weir inaccordance with the first aspect of the invention and the invention thusprovides an installation comprising a self-regulating weir and aself-regulating fishway, each having the features defined above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the principles of operation of a self-regulatingcounterbalanced weir,

FIG. 2 is a side elevation of the tilting weir of the present invention,

FIG. 3 is an upstream elevation of the weir shown in FIG. 2,

FIG. 4 is a plan/sectional view along the line A—A of FIG. 3,

FIG. 5 is a sectional view along the line B—B of FIG. 4,

FIG. 6 is a sectional view along the line C—C of FIG. 3,

FIG. 7 is a sectional view along the line D—D of FIG. 3,

FIG. 8 is an upstream isometric view of the weir of FIG. 2,

FIG. 9 is a sectional view of the fishway,

FIG. 10 is a plan view of the fishway,

FIG. 11 is a cross-sectional view of the fishway, and

FIG. 12 is a pictorial view showing the fishway of FIGS. 9, 10 and 11located alongside the weir of FIGS. 2 to 8.

BRIEF DESCRIPTION OF THE DRAWINGS

As shown in FIG. 1, quadrilaterals A-B-C-P and A1-B1-C1-P haveperimeters of equal length with point P being a fixed location.

A-P and P-C are equal in length with a fixed dimension.

Point B can be moved vertically in a straight line towards or away frompoint P so as to alter the location of A to A1 and B to B1, or anyposition in between.

Individual dimensions A-B, B-C , A1-B1 and B1-C1 can vary, but the totaldistance A-B-C is constant and equal to A1-B1-C1.

APPLICATION OF THE PRINCIPLE

Weir A-P pivots about point P and is controlled by the floatingcounterbalance C via the flexible connection A-B-C. Counterbalance C isheld at a constant distance from point P by a strut P-C which has alength equal to that of the weir A-P.

Pulley wheel at point B is vertically adjustable within prescribedlimits to suit the needs of the design and flexible connection A-B-C isfree to traverse point B allowing the counterbalance C to control theposition of the weir A-P at all times. Adjustment of the automaticallymaintained water level is achieved by raising or lowering the pulleywheel at point B as appropriate.

It will thus be seen that the application of the principles outlinedabove provides automatic self-regulation with mechanical simplicity andadjustment by one simple operation.

FIGS. 2 to 8 show the self-regulating tilting weir in a medianregulating position, the weir maintaining the upstream water at arequired level by the action of the floating counterbalance weights. Ifthe upstream water level falls, the floating counterbalance weights willfollow and lift the weir accordingly, thus damming the flow to restorethe required level upstream of the weir. If the upstream water levelrises, the floating counterbalance weights will follow and will lowerthe weir accordingly, thus releasing greater flow to restore therequired upstream level.

In times of drought or flash flood, the weir will close or open to itsrespective extreme limits. Floating material tending to clog the weirwill cause the weir plate to fall as the upstream level rises and theincreased flow will then force the detritus on downstream. Any build-upof silt can be flushed downstream by lowering the weir manually to thebottom limit. In an emergency situation, the weir can be closed oropened manually by raising or lowering the weir to the relevant extremelimit.

The weir of the present invention (the construction and mode ofoperation of which will now be described in detail with reference toFIGS. 2 to 8) thus satisfies requirements a) to k) referred to in theintroduction, and the requirement I), i.e. to cater for migratory fishmovement, is dealt with by the use of the fishway described below indetail with reference to FIGS. 9 and 10.

As shown in FIGS. 2 to 8, the self-regulating weir comprises a generallyrectangular frame 1 and a tilting weir plate with vertical sides 2.Means (not shown) are provided for sealing the weir plate against theframe 1 so that there is no substantial water flow between the weirplate and the frame 1. The weir plate is hinge mounted on the base ofthe support frame 1 at the invert end 3 and is counterbalanced byfloating weights 4. The floating weights 4 are held in place by struts12 which are hinged at one end at invert level 3 and are hinged andadjustably connected at their other ends 13 to the floating weights 4.

In the particular arrangement shown in the drawings, two counterbalanceweights are connected to each other by a distance piece 14. The number,weight and positions of the counterbalances may, however, be varied asrequired, to suit the particular location and operating parameters.

The floating weights 4 are also connected, by chains or cables 5 to theweir plate, the chains or cables 5 passing over freely rotating pulleywheels 6 which are mounted on vertically sliding lifting blocks 7. Thelifting blocks 7 can be raised or lowered in tandem by lift spindles 8which are operated by a removable hand crank 15 via a worm gear 11turning a pair of lift nuts 10 mounted on thrust blocks 9 attached tothe frame 1. The hand crank 15 can be removed for security. The mode ofoperation of the weir by means of the hand crank 15 provides a means foroperating the weir manually overriding the automatic action and enablingthe weir to be fixed in, for example, its fully open or its fully closedposition as required, regardless of the flow conditions.

The pulley wheels 6 and their lifting gear are clear of the watersurface at all possible degrees of weir opening, thus avoiding clogging.The upstream edges of the tilting weir and the ends of the floatingcounterbalance weights 4 can be profiled to reduce clogging by anyfloating material and to improve flow through the weir. The curvedprofile will be determined by the material of manufacture. The materialused for the sides of the weir plate will determine how a curve awayfrom the direction of flow can be provided The horizontal top member ofthe frame 1 is bolted to the vertical side members to allow for completeaccess to the lifting gear, should this be necessary.

FIGS. 9, 10 and 11 are views of a self-regulating fishway. The upstreamwater level is regulated so that the maximum recommended incline is notexceeded for the specific fish pass profile which is utilised. Theconstruction of the fishway is such that, by action of its floats, theself-regulating fishway automatically adjusts its upstream sill level tothe required depth relative to the upstream water level. The water thenflows down the self-regulating fishway at the required depth to suit thefish pass profile that is being employed.

The lower end of the fishway is constantly immersed below the downstreamwater level, being so designed as to be of sufficient length to ensure acontinuous water link between the regulated upstream level and thelowest predicted downstream level, thus preserving continuousfish-attracting flow. The lower end of the fishway also acts as apartial counter-balance, reducing the design size of the upstream floator floats.

Referring now specifically to FIGS. 9, 10 and 11, these show aself-regulating fishway which comprises a rectangular frame 21 set in aheadwall 22 and a rectangular section tilting chute 23. A fish passprofile 24 is fitted in the chute 23 which is pivotally connected at 25to the frame 21. Commercially available rubber profiles 26 are used toseal the pivot shaft and chute sides to the frame 21. Cables 30 may alsobe used to connect the upper end of the fishway to the headwall or otherconvenient point to maintain the desired alignment with the upstreamflow.

A bulb profile 27 is provided at the upper or upstream end of the chute23 and may incorporate one or more floats. Each float may be partiallyfilled with water, the bulb 27 and floats being interconnected tomaintain level filling using the generally U-shaped filler/air bleedpipes 28.

The self-regulating fishway shown in FIGS. 9, 10 and 11 provides theaverage incline, water velocity and fish-attracting flow features neededfor the specified fish pass profile 24, by maintaining the upstreamentrance sill level at the required depth relative to the upstream waterlevel and a continuous water link with the lowest predicted water levelat the downstream entrance. The fishway will not use more water than isrequired by the fish pass profile 24 and flow for the specified fishpass profile is available continuously, providing a constant water linkand exit water velocity sufficient to attract the required fish speciesat all times. Self-regulation of the fishway minimises operation costsand the fishway is of modular form allowing prefabrication off-siteusing stainless steel or synthetic plastic materials, thus reducingconstruction and maintenance costs. Floating debris tends to be divertedby the bulb action on the flow.

Site factors and the required fish pass profile dictate dimensions asfollows:

1) maximum/minimum angle of incline α,

2) minimum width and height b of chute 23,

3) maximum/minimum upstream water level c,

4) water depth d over fishway entrance sill,

5) size e of the bulb 27 and the float or floats, and

6) lengths f of the upstream and downstream sections of the chute 23,and

7) the upstream projection g of the bulb 27.

The self-regulating weir of FIGS. 2 to 8 working in parallel with theself-regulating fishway of FIGS. 9 to 11 offers reasonably accurate andflexible controls of relative levels and flow for the benefit ofmigratory fish.

What is claimed is:
 1. A counterbalanced, self-regulating tilting weircomprising a tiltable weir gate over which the water flows, the weirgate being hinged at its lower edge to the base of a support frame andcounterbalanced by float means located upstream of the weir gate so thatthe level of the weir is raised in response to a fall in the water levelupstream of the weir gate, the weir gate being connected to the floatmeans by chains or cables which pass over pulley wheels, and means beingprovided for effecting vertical movement of the pulley wheels relativeto the support frame.
 2. A weir as claimed in claim 1, in which themeans for effecting vertical movement of the pulley wheels comprisevertical lift spindles.
 3. A weir as claimed in claim 2, in which thevertical lift spindles are operated, via a worm gear, by means of aremovable hand crank.
 4. A weir as claimed in claim 1, in which meansare provided for adjustment of operating angles of the chains or cables.5. A weir as claimed in claim 1, in which means are provided foroperating the weir manually, overriding automatic action and fixing theweir either fully open or fully closed as required, regardless of flowconditions.
 6. A weir as claimed in claim 1, in combination with aself-regulating fishway comprising a tiltable chute containing a fishpass profile, the chute being arranged for tilting movement by one ormore floats positioned at or adjacent to the upstream end of the chuteso that required relative water level is maintained at the chuteentrance, the upstream water level being so regulated by the weir thatthe chute incline does not exceed a maximum desirable level for aspecific fish pass profile which is used.
 7. The combination of a weirand fishway as claimed in claim 6, in which the float or floats at theupstream end of the chute incorporate a submersed buoyant bulb profileextending upstream of the chute entrance.
 8. The combination of a weirand fishway as claimed in claim 7, in which cables are attached to bothsides of the upstream end of the chute in order to maintain a desiredalignment of the fishway with a normal flow.